/*
 * ice4j, the OpenSource Java Solution for NAT and Firewall Traversal.
 *
 * Copyright @ 2015 Atlassian Pty Ltd
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.ice4j.attribute;

import org.ice4j.StunException;

import java.util.Arrays;

/**
 * The NONCE attribute is used for authentication.
 *
 * @author Sebastien Vincent
 */
public class NonceAttribute extends Attribute {
	/**
	 * Attribute name.
	 */
	public static final String NAME = "NONCE";

	/**
	 * Nonce value.
	 */
	private byte nonce[] = null;

	/**
	 * Constructor.
	 */
	NonceAttribute() {
		super(NONCE);
	}

	/**
	 * Copies the value of the nonce attribute from the specified
	 * attributeValue.
	 * 
	 * @param attributeValue
	 *            a binary array containing this attribute's field values and
	 *            NOT containing the attribute header.
	 * @param offset
	 *            the position where attribute values begin (most often offset
	 *            is equal to the index of the first byte after length)
	 * @param length
	 *            the length of the binary array.
	 * @throws StunException
	 *             if attributeValue contains invalid data.
	 */
	void decodeAttributeBody(byte[] attributeValue, char offset, char length) throws StunException {
		nonce = new byte[length];
		System.arraycopy(attributeValue, offset, nonce, 0, length);
	}

	/**
	 * Returns a binary representation of this attribute.
	 * 
	 * @return a binary representation of this attribute.
	 */
	public byte[] encode() {
		char type = getAttributeType();
		byte binValue[] = new byte[HEADER_LENGTH + getDataLength() + (getDataLength() % 4)];

		// Type
		binValue[0] = (byte) (type >> 8);
		binValue[1] = (byte) (type & 0x00FF);

		// Length
		binValue[2] = (byte) (getDataLength() >> 8);
		binValue[3] = (byte) (getDataLength() & 0x00FF);

		/* nonce */
		System.arraycopy(nonce, 0, binValue, 4, (int) getDataLength());

		return binValue;
	}

	/**
	 * Returns the length of this attribute's body.
	 * 
	 * @return the length of this attribute's value.
	 */
	public char getDataLength() {
		return (char) nonce.length;
	}

	/**
	 * Returns the human readable name of this attribute.
	 * 
	 * @return this attribute's name.
	 */
	public String getName() {
		return NAME;
	}

	/**
	 * Returns a (cloned) byte array containing the data value of the nonce
	 * attribute.
	 * 
	 * @return the binary array containing the nonce.
	 */
	public byte[] getNonce() {
		return (nonce == null) ? null : nonce.clone();
	}

	/**
	 * Copies the specified binary array into the the data value of the nonce
	 * attribute.
	 * 
	 * @param nonce
	 *            the binary array containing the nonce.
	 */
	public void setNonce(byte[] nonce) {
		this.nonce = (nonce == null) ? null : nonce.clone();
	}

	/**
	 * Compares two STUN Attributes. Two attributes are considered equal when
	 * they have the same type length and value.
	 * 
	 * @param obj
	 *            the object to compare this attribute with.
	 * @return true if the attributes are equal and false otherwise.
	 */
	public boolean equals(Object obj) {
		if (obj == this)
			return true;
		if (!(obj instanceof NonceAttribute))
			return false;

		NonceAttribute att = (NonceAttribute) obj;

		return (att.getAttributeType() == getAttributeType() && att.getDataLength() == getDataLength()
				&& Arrays.equals(att.nonce, nonce));
	}
}
